U.S. patent application number 15/920333 was filed with the patent office on 2018-10-04 for wavelength conversion element, light source apparatus, and projector.
This patent application is currently assigned to SEIKO EPSON CORPORATION. The applicant listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Yoshitaka ITOH.
Application Number | 20180284584 15/920333 |
Document ID | / |
Family ID | 63669240 |
Filed Date | 2018-10-04 |
United States Patent
Application |
20180284584 |
Kind Code |
A1 |
ITOH; Yoshitaka |
October 4, 2018 |
WAVELENGTH CONVERSION ELEMENT, LIGHT SOURCE APPARATUS, AND
PROJECTOR
Abstract
A wavelength conversion element according to an aspect of the
invention includes a wavelength conversion section having a first
surface, a reflection section having a reflection surface that
reflects the fluorescence, a light-transparent bonding section that
bonds the wavelength conversion section to the reflection section,
and a refractive index interface which is provided between the
first surface and the reflection surface and where a first medium
and a second medium having refractive indices different from each
other are in contact with each other. The refractive index of the
first medium is higher than the refractive index of the second
medium, and regarding the fluorescence traveling from the
wavelength conversion section toward the reflection section, the
angular distribution of the fluorescence having passed through the
refractive index interface is narrower than the angular
distribution of the fluorescence before passing through the
refractive index interface.
Inventors: |
ITOH; Yoshitaka;
(Matsumoto-Shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
63669240 |
Appl. No.: |
15/920333 |
Filed: |
March 13, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03B 21/208 20130101;
F21S 41/285 20180101; F21S 41/16 20180101; F21S 41/176 20180101;
G03B 21/2053 20130101; G03B 21/204 20130101 |
International
Class: |
G03B 21/20 20060101
G03B021/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2017 |
JP |
2017-063251 |
Claims
1. A wavelength conversion element comprising: a wavelength
conversion section having a first surface on which excitation light
is incident and through which fluorescence exits; a reflection
section having a reflection surface that reflects the fluorescence;
a light-transparent bonding section that bonds the wavelength
conversion section to the reflection section; and a refractive
index interface which is provided between the first surface and the
reflection surface and where a first medium and a second medium
having refractive indices different from each other are in contact
with each other, wherein the refractive index of the first medium
located on the-first-surface-side of the refractive index interface
is higher than the refractive index of the second medium located on
the reflection-surface-side of the refractive index interface, and
regarding the fluorescence traveling from the wavelength conversion
section toward the reflection section, an angular distribution of
the fluorescence having passed through the refractive index
interface is narrower than the angular distribution of the
fluorescence before passing through the refractive index
interface.
2. The wavelength conversion element according to claim 1, wherein
the refractive index interface is formed of a second surface of the
wavelength conversion section that is a surface opposite the first
surface thereof or a first surface of the bonding section that is a
surface located on a side facing the wavelength conversion
section.
3. The wavelength conversion element according to claim 2, further
comprising a first refractive index section provided between the
wavelength conversion section and the bonding section, wherein the
wavelength conversion section is made of the first medium, and the
first refractive index section is made of the second medium.
4. The wavelength conversion element according to claim 2, further
comprising a second refractive index section provided between the
wavelength conversion section and the bonding section, wherein the
second refractive index section is made of the first medium, and
the bonding section is made of the second medium.
5. The wavelength conversion element according to claim 1, further
comprising a first refractive index section so provided between the
wavelength conversion section and the bonding section as to be in
contact with the bonding section; and a second refractive index
section so provided between the wavelength conversion section and
the bonding section as to be in contact with the wavelength
conversion section, wherein the first refractive index section is
made of the second medium, and the second refractive index section
is made of the first medium.
6. The wavelength conversion element according to claim 1, wherein
the refractive index interface has a shape containing a plurality
of pyramids.
7. The wavelength conversion element according to claim 6, wherein
a bottom surface of each of the pyramids has a polygonal shape.
8. The wavelength conversion element according to claim 1, wherein
the reflection section is formed of a dielectric multilayer
film.
9. The wavelength conversion element according to claim 1, further
comprising a substrate so provided as to be in contact with the
reflection section.
10. A light source apparatus comprising: the wavelength conversion
element according to claim 1; and an excitation light source that
emits the excitation light.
11. A light source apparatus comprising: the wavelength conversion
element according to claim 2; and an excitation light source that
emits the excitation light.
12. A light source apparatus comprising: the wavelength conversion
element according to claim 3; and an excitation light source that
emits the excitation light.
13. A light source apparatus comprising: the wavelength conversion
element according to claim 4; and an excitation light source that
emits the excitation light.
14. A light source apparatus comprising: the wavelength conversion
element according to claim 5; and an excitation light source that
emits the excitation light.
15. A light source apparatus comprising: the wavelength conversion
element according to claim 6; and an excitation light source that
emits the excitation light.
16. A projector comprising: the light source apparatus according to
claim 10; a light modulator that modulates light from the light
source apparatus in accordance with image information to form image
light; and a projection system that projects the image light.
17. A projector comprising: the light source apparatus according to
claim 11; a light modulator that modulates light from the light
source apparatus in accordance with image information to form image
light; and a projection system that projects the image light.
18. A projector comprising: the light source apparatus according to
claim 12; a light modulator that modulates light from the light
source apparatus in accordance with image information to form image
light; and a projection system that projects the image light.
19. A projector comprising: the light source apparatus according to
claim 13; a light modulator that modulates light from the light
source apparatus in accordance with image information to form image
light; and a projection system that projects the image light.
20. A projector comprising: the light source apparatus according to
claim 14; a light modulator that modulates light from the light
source apparatus in accordance with image information to form image
light; and a projection system that projects the image light.
Description
BACKGROUND
1. Technical Field
[0001] The present invention relates to a wavelength conversion
element, a light source apparatus, and a projector.
2. Related Art
[0002] In a projector, a light source apparatus capable of
outputting high-intensity light is required to increase the
luminance of a projected image. To this end, a light source
apparatus including an excitation light source and a wavelength
conversion element has been recently proposed. In the light source
apparatus, the wavelength conversion element is irradiated with
excitation light emitted from the excitation light source, such as
a semiconductor laser or a light emitting diode, to produce
fluorescence, which is used as part of illumination light.
[0003] For example, JP-A-2012-27052 discloses a light source
apparatus including lasers, a fluorescing substrate that is
irradiated with blue light to produce green or red light, and a
quadrangular pyramidal prism array on which the light from the
fluorescing substrate is incident. JP-A-2012-27052 describes that
the fluorescence orientation directivity is improved by causing the
fluorescence to undergo multiple reflection between the fluorescing
substrate and the prism array.
[0004] JP-A-2011-53320 discloses a light source apparatus including
an excitation light source that outputs blue light and a
fluorescing wheel that is irradiated with the blue light to produce
green light. JP-A-2011-53320 describes that high-intensity
fluorescence is produced by optimizing the weight concentration of
a phosphor contained in a phosphor layer and the film thickness of
the phosphor with respect to the thickness of the phosphor
layer.
[0005] A wavelength conversion element, such as a fluorescing
substrate, is classified into a transmissive wavelength conversion
element that emits fluorescence through the surface opposite the
surface on which excitation light is incident and a reflective
wavelength conversion element that emits fluorescence through the
surface on which excitation light is incident.
[0006] In general, a phosphor is characterized in that its light
emission efficiency decreases as the temperature increases. The
light source apparatus described in JP-A-2012-27052, in which a
transmissive wavelength conversion element is used, has a problem
of difficulty in efficiently dissipating heat generated in a
phosphor layer. Therefore, even if the fluorescence orientation
directivity can be improved, high light emission efficiency cannot
be achieved, and it is therefore difficult to achieve a wavelength
conversion element capable of producing high-intensity
fluorescence.
[0007] On the other hand, in the light source apparatus described
in JP-A-2011-53320, in which the fluorescing wheel is so configured
that the area where the phosphor layer is formed has a reflective
structure but the area where the blue light is diffused has a
transmissive structure, it is difficult for the fluorescing wheel
as a whole to dissipate the heat from the phosphor layer.
[0008] Further, the fluorescing wheel in JP-A-2011-53320 has a
configuration in which a reflection surface made, for example, of
silver, a transparent protective film made, for example, of
magnesium fluoride, and the phosphor layer are sequentially layered
on a metal substrate. To achieve high-optical-intensity
fluorescence, it is important to increase the amount of light
reflected off the reflection surface described above and traveling
in the direction opposite the direction in which the excitation
light is incident. To increase the amount of the fluorescence
reflected off the reflection surface, it is effective to increase
the reflectance at the reflection surface.
[0009] In the case where the reflection surface is formed by using
silver, as in JP-A-2011-53320, high reflectance is achieved, but
there are the following problems: Reflection loss of about 3 to 5%
occurs; and the reflectance lowers when the angle of incidence
increases. Further, the silver absorbs the light and generates
heat, resulting in degradation of the silver due to thermal
oxidation. A reflection surface made of silver has a variety of
problems, such as those described above, and it is undesirably
difficult to increase the reflectance.
SUMMARY
[0010] An advantage of some aspects of the invention is to provide
a wavelength conversion element capable of increasing the amount of
fluorescence reflected off a reflection surface as compared with
the amount in related art to produce high-optical-intensity
fluorescence. Another advantage of some aspects of the invention is
to provide a light source apparatus including the wavelength
conversion element. Still another advantage of some aspects of the
invention is to provide a projector including the light source
apparatus.
[0011] A wavelength conversion element according to an aspect of
the invention includes a wavelength conversion section having a
first surface on which excitation light is incident and through
which fluorescence exits, a reflection section having a reflection
surface that reflects the fluorescence, a light-transparent bonding
section that bonds the wavelength conversion section to the
reflection section, and a refractive index interface which is
provided between the first surface and the reflection surface and
where a first medium and a second medium having refractive indices
different from each other are in contact with each other. The
refractive index of the first medium located on
the-first-surface-side of the refractive index interface is higher
than the refractive index of the second medium located on the
reflection-surface-side of the refractive index interface, and
regarding the fluorescence traveling from the wavelength conversion
section toward the reflection section, an angular distribution of
the fluorescence having passed through the refractive index
interface is narrower than the angular distribution of the
fluorescence before passing through the refractive index
interface.
[0012] In the wavelength conversion element according to the aspect
of the invention, regarding the fluorescence traveling from the
wavelength conversion section toward the reflection section, the
angular distribution of the fluorescence having passed through the
refractive index interface is narrower than the angular
distribution of the fluorescence before passing through the
refractive index interface, whereby the reflectance at the
reflection surface can be increased, and the amount of fluorescence
reflected off the reflection surface can therefore be increased. A
wavelength conversion element capable of producing
high-optical-intensity fluorescence can thus be achieved.
[0013] In the wavelength conversion element according to the aspect
of the invention, the refractive index interface maybe formed of a
second surface of the wavelength conversion section that is a
surface opposite the first surface thereof or a first surface of
the bonding section that is a surface located on a side facing the
wavelength conversion section.
[0014] According to the configuration described above, the
refractive index interface can be the second surface of the
wavelength conversion section that is the surface opposite the
first surface thereof or the first surface of the bonding section
that is a surface located on the side facing the wavelength
conversion section. A simply structured wavelength conversion
element can therefore be provided.
[0015] The wavelength conversion element according to the aspect of
the invention may further include a first refractive index section
provided between the wavelength conversion section and the bonding
section. In this case, the wavelength conversion section may be
made of the first medium, and the first refractive index section
may be made of the second medium.
[0016] According to the configuration described above, the surface
where the wavelength conversion section is in contact with the
first refractive index section can be the refractive index
interface. In this case, appropriately selecting the second medium
to adjust the refractive index of the first refractive index
section allows control of the angular distribution of the
fluorescence having passed through the refractive index
interface.
[0017] The wavelength conversion element according to the aspect of
the invention may further include a second refractive index section
provided between the wavelength conversion section and the bonding
section. In this case, the second refractive index section may be
made of the first medium, and the bonding section may be made of
the second medium.
[0018] According to the configuration described above, the surface
where the second refractive index section is in contact with the
bonding section can be the refractive index interface. In this
case, appropriately selecting the first medium to adjust the
refractive index of the second refractive index section allows
control of the angular distribution of the fluorescence having
passed through the refractive index interface.
[0019] The wavelength conversion element according to the aspect of
the invention may further include a first refractive index section
so provided between the wavelength conversion section and the
bonding section as to be in contact with the bonding section and a
second refractive index section so provided between the wavelength
conversion section and the bonding section as to be in contact with
the wavelength conversion section. In this case, the first
refractive index section may be made of the second medium, and the
second refractive index section may be made of the first
medium.
[0020] According to the configuration described above, the surface
where the first refractive index section is in contact with the
second refractive index section can be the refractive index
interface. In this case, appropriately selecting the first and
second media to adjust the refractive indices of the first and
second refractive index sections allows control of the angular
distribution of the fluorescence having passed through the
refractive index interface.
[0021] In the wavelength conversion element according to the aspect
of the invention, the refractive index interface may have a shape
containing a plurality of pyramids.
[0022] According to the configuration described above, when the
fluorescence passes through the refractive index interface having
the shape containing the plurality of pyramids, the proportion of
the fluorescence that is incident on the reflection surface of the
reflection section at small angles of incidence can be
increased.
[0023] In the wavelength conversion element according to the aspect
of the invention, a bottom surface of each of the pyramids may have
a polygonal shape.
[0024] According to the configuration described above, optimally
designing the polygonal shape allows the plurality of pyramids to
be arranged in a closest packing state. The effect of increasing
the proportion of the fluorescence that is incident on the
reflection surface at small angles of incidence can therefore be
maximized.
[0025] In the wavelength conversion element according to the aspect
of the invention, the reflection section may be formed of a
dielectric multilayer film.
[0026] In general, a dielectric multilayer film has a high
dependence of the reflectance on the angle of incidence but is
likely to achieve high reflectance as compared with a metal film in
a region of a narrow incident angle range. In the wavelength
conversion element according to the aspect of the invention, the
angle of incidence of the fluorescence with respect to the
reflection surface can be reduced, so that the incident angle range
can be narrowed, as described above, whereby the reflectance of the
fluorescence can be increased by making use of the characteristics
of a dielectric multilayer film.
[0027] The wavelength conversion element according to the aspect of
the invention may further include a substrate so provided as to be
in contact with the reflection section.
[0028] According to the configuration described above, the
substrate can support the laminate of the wavelength conversion
section, the reflection section, and other components, and
selecting a substrate having high thermal conductivity allows
enhancement of the heat dissipation capability of the wavelength
conversion element.
[0029] A light source apparatus according to another aspect of the
invention includes the wavelength conversion element according to
the aspect of the invention and an excitation light source that
emits the excitation light.
[0030] According to the configuration described above,
high-optical-intensity fluorescence is achieved, whereby a
high-intensity light source apparatus can be provided.
[0031] A projector according to another aspect of the invention
includes the light source apparatus according to the aspect of the
invention, a light modulator that modulates light from the light
source apparatus in accordance with image information to form image
light, and a projection system that projects the image light.
[0032] According to the configuration described above, since the
light source apparatus capable of producing high-optical-intensity
fluorescence is used, a projector capable of producing a
high-luminance projection image can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0034] FIG. 1 is a schematic configuration diagram of a projector
according to a first embodiment.
[0035] FIG. 2 is a cross-sectional view of a wavelength conversion
element according to the first embodiment.
[0036] FIG. 3A is a perspective view of a plurality of prism
structures.
[0037] FIG. 3B is a plan view of the plurality of prism structures
viewed in the direction of a normal to a reflection surface.
[0038] FIG. 4A is a perspective view of a prism structure in a
variation.
[0039] FIG. 4B is a plan view of the prism structure in the
variation viewed in the direction of a normal to the reflection
surface.
[0040] FIG. 5 describes the operation of the wavelength conversion
element.
[0041] FIG. 6 is a plan view of a wavelength conversion apparatus
viewed in the direction of a normal to a substrate.
[0042] FIG. 7 is a cross-sectional view of a wavelength conversion
element according to a second embodiment.
[0043] FIG. 8 is a cross-sectional view of a wavelength conversion
element according to a third embodiment.
[0044] FIG. 9 is a cross-sectional view of a wavelength conversion
element according to a fourth embodiment.
[0045] FIG. 10 is a schematic configuration diagram of a projector
according to a fifth embodiment.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
First Embodiment
[0046] A first embodiment of the invention will be described below
with reference to FIGS. 1 to 6.
[0047] A projector according to the present embodiment is an
example of a liquid crystal projector including a semiconductor
laser and a wavelength conversion element.
[0048] In the following drawings, components are drawn at different
dimensional scales in some cases for clarity of each of the
components.
[0049] The projector according to the present embodiment is a
projection-type image display apparatus that displays color video
images on a screen (projection surface). The projector uses three
light modulators corresponding to color light fluxes, red light,
green light, and blue light. The projector uses, as a light
emitting device of the light source apparatus, a semiconductor
laser (laser diode) capable of emitting high-luminance,
high-intensity light.
[0050] FIG. 1 is a schematic configuration diagram of the projector
according to the present embodiment.
[0051] A projector 1 includes a first light source apparatus 100
(light source apparatus), a second light source apparatus 102, a
light separation/light guide system 200, a light modulator 400R, a
light modulator 400G, a light modulator 400B, a light combining
system 500, and a projection system 600, as shown in FIG. 1.
[0052] The first light source apparatus 100 according to the
present embodiment corresponds to the light source apparatus in the
appended claims.
[0053] The light source apparatus 100 includes a first light
emitting device 10, a collimation system 70, a dichroic mirror 80,
a collimation/light collection system 90, a wavelength conversion
apparatus 20, a homogenizer system 125, a polarization conversion
element 140, and a superimposing lens 150. The wavelength
conversion apparatus 20 will be described later in detail.
[0054] The first light emitting device 10 is formed of a
semiconductor laser that emits blue excitation light E. The
intensity of the emitted excitation light E peaks, for example, at
a wavelength of 445 nm. The first light emitting device 10 may be
formed of one semiconductor laser or a plurality of semiconductor
lasers. The first light emitting device 10 may instead be formed of
a semiconductor laser that emits blue light having a wavelength
different from 445 nm (460 nm, for example). The first light
emitting device 10 is so disposed that the optical axis 110ax
thereof is perpendicular to an illumination optical axis 100ax.
[0055] The first light emitting device 10 in the present embodiment
corresponds to an excitation light source in the appended
claims.
[0056] The collimation system 70 includes a first lens 72 and a
second lens 74. The collimation system 70 roughly parallelizes the
light emitted from the first light emitting device 10. The first
lens 72 and the second lens 74 are each formed of a convex
lens.
[0057] The dichroic mirror 80 is provided in the optical path from
the collimation system 70 to the collimation/light collection
system 90. The dichroic mirror 80 is so disposed as to incline by
45.degree. with respect to the optical axis 110ax of the first
light emitting device 10 and the illumination optical axis 100ax.
The dichroic mirror 80 reflects light that belongs to a blue
wavelength region and transmits light that belongs to a yellow
wavelength region containing red light and green light.
[0058] The collimation/light collection system 90 has the function
of causing the excitation light E having exited out of the dichroic
mirror 80 to be incident on a wavelength conversion element 21 with
the excitation light E roughly focused and the function of roughly
parallelizing fluorescence Y emitted from the wavelength conversion
element 21. The collimation/light collection system 90 includes a
first lens 92 and a second lens 94. The first lens 92 and the
second lens 94 are each formed of a convex lens.
[0059] The second light source apparatus 102 includes a second
light emitting device 710, a light collection system 760, a
diffuser plate 732, and a collimation system 770.
[0060] The second light emitting device 710 is formed of a
semiconductor laser that emits blue light B. The intensity of the
emitted blue light B peaks, for example, at a wavelength of 460 nm,
which is different from the wavelength at which the intensity of
the excitation light E emitted from the first light emitting device
10 peaks. The second light emitting device 710 may instead be
formed of a semiconductor laser that emits light having intensity
that peaks at the same wavelength at which the intensity of the
excitation light E emitted from the first light emitting device 10
peaks.
[0061] The light collection system 760 includes a first lens 762
and a second lens 764. The light collection system 760 collects the
blue light B emitted from the second light emitting device 710 in
the vicinity of the diffuser plate 732. The first lens 762 and the
second lens 764 are each formed of a convex lens.
[0062] The diffuser plate 732 diffuses the blue light B emitted
from the second light emitting device 710 into blue light B having
a light orientation distribution similar to the light orientation
distribution of the fluorescence Y emitted from the wavelength
conversion apparatus 20. The diffuser plate 732 can, for example,
be a ground glass plate made of optical glass.
[0063] The collimation system 770 includes a first lens 772 and a
second lens 774. The collimation system 770 roughly parallelizes
the light having exited out of the diffuser plate 732. The first
lens 772 and the second lens 774 are each formed of a convex
lens.
[0064] The blue light B outputted from the second light source
apparatus 102 is reflected off the dichroic mirror 80 and then
combined with the fluorescence Y having passed through the dichroic
mirror 80 into white illumination light W. The illumination light W
enters the homogenizer system 125.
[0065] The homogenizer system 125 includes a first lens array 120
and a second lens array 130. The first lens array 120 includes a
plurality of first lenses 122 for dividing the light outputted
having exited out of the dichroic mirror 80 into a plurality of
sub-light fluxes. The plurality of first lenses 122 are arranged in
a matrix in a plane perpendicular to the illumination optical axis
100ax.
[0066] The second lens array 130 includes a plurality of second
lenses 132 corresponding to the plurality of first lenses 122 in
the first lens array 120. The second lens array 130, along with the
superimposing lens 150, forms images of the first lenses 122 in the
first lens array 120 in the vicinity of an image formation area of
each of the light modulators 400R, 400G, and 400B. The plurality of
second lenses 132 are arranged in a matrix in a plane perpendicular
to the illumination optical axis 100ax.
[0067] The polarization conversion element 140 converts each of the
divided sub-light ray fluxes from the first lens array 120 into a
linearly polarized light. The polarization conversion element 140
includes polarization separation layers, reflection layers, and
retardation layers, although not shown in detail. The polarization
separation layers directly transmit one linearly polarized light
component of the polarized light components contained in the light
from the wavelength conversion apparatus 20 and reflect another
linearly polarized light component in the direction perpendicular
to the illumination optical axis 100ax. The reflection layers
reflect the other linearly polarized light component reflected off
the polarization separation layers in the direction parallel to the
illumination optical axis 100ax. The retardation layers convert the
other linearly polarized light component reflected off the
reflection layers into the one linearly polarized light
component.
[0068] The superimposing lens 150 collects the sub-light ray fluxes
from the polarization conversion element 140 and superimposes the
sub-light ray fluxes on one another in the vicinity of the image
formation area of each of the light modulators 400R, 400G, and
400B. The first lens array 120, the second lens array 130, and the
superimposing lens 150 homogenize the in-plane optical intensity
distribution of the light outputted from the wavelength conversion
apparatus 20.
[0069] The color separation/light guide system 200 separates the
white illumination light W into the red light L, the green light G,
and the blue light B. The color separation/light guide system 200
includes a first dichroic mirror 210, a second dichroic mirror 220,
a first reflection mirror 230, a second reflection mirror 240, a
third reflection mirror 250, a first relay lens 260, and a second
relay lens 270.
[0070] The first dichroic mirror 210 has the function of separating
the illumination light W outputted from the first light source
apparatus 100 into the red light and the other light (green light G
and blue light B). The first dichroic mirror 210 transmits the red
light R and reflects the other light (green light G and blue light
B). On the other hand, the second dichroic mirror 220 has the
function of separating the other light into the green light G and
the blue light B. The second dichroic mirror 220 reflects the green
light G and transmits the blue light B.
[0071] The first reflection mirror 230 is disposed in the optical
path of the red light R and reflects the red light R having passed
through the first dichroic mirror 210 toward the light modulator
400R. The second reflection mirror 240 and the third reflection
mirror 250 are disposed in the optical path of the blue light B and
reflect the blue light B having passed through the second dichroic
mirror 220 toward the light modulator 400B. The green light G is
reflected off the second dichroic mirror 220 toward the light
modulator 400G.
[0072] The first relay lens 260 and the second relay lens 270 are
disposed in the optical path of the blue light B and on the light
exiting side of the second dichroic mirror 220. The first relay
lens 260 and the second relay lens 270 have the function of
compensating loss of the blue light B due to the fact that the
optical path of the blue light B is longer than the optical paths
of the red light R and the green light G.
[0073] The light modulator 400R modulates the red light R in
accordance with image information to form image light corresponding
to the red light R. The light modulator 400G modulates the green
light G in accordance with image information to form image light
corresponding to the green light G. The light modulator 400B
modulates the blue light B in accordance with image information to
form image light corresponding to the blue light B.
[0074] A transmissive liquid crystal panel is, for example, used as
each of the light modulators 400R, 400G, and 400B. A pair of
polarizers (not shown) are disposed on the light incident side and
light exiting side of each of the liquid crystal panels and
configured to transmit only light linearly polarized in a specific
direction.
[0075] Field lenses 300R, 300G, and 300B are disposed on the light
incident side of the light modulators 400R, 400G, and 400B,
respectively. The field lenses 300R, 300G, and 300B parallelize the
red light R, the green light G, and the blue light B to be incident
on the light modulators 400R, 400G, and 400B, respectively.
[0076] The light combining system 500 combines the image light
fluxes incident thereon from the light modulators 400R, 400G, and
400B with one another into image light corresponding to the red
light R, the green light G, and the blue light B and causes the
combined image light to exit toward the projection system 600.
Across dichroic prism is, for example, used as the light combining
system 500.
[0077] The projection system 600 is formed of a projection lens
group 6. The projection system 600 enlarges the combined image
light from the light combining system 500 and projects the enlarged
image light toward a screen SCR. An enlarged color video (images)
is thus displayed on the screen SCR.
[0078] The configuration of the wavelength conversion apparatus 20
will be described below.
[0079] FIG. 2 is a cross-sectional view of the wavelength
conversion element 21 and is an enlarged view of the portion
labeled with the reference character A in FIG. 1.
[0080] FIG. 6 is a plan view of the wavelength conversion apparatus
20 viewed in the direction of a normal to a substrate 24.
[0081] The wavelength conversion apparatus 20 includes the
wavelength conversion element 21, which has a disk-like shape, and
a motor 22, which rotates the wavelength conversion element 21, as
shown in FIGS. 2 and 6. The configuration of the wavelength
conversion element 21 will be described later in detail. In FIG. 1,
the components of the wavelength conversion element 21 are omitted
as appropriate for ease of illustration.
[0082] The wavelength conversion element 21 rotates around a rotary
shaft 23 when driven with the motor 22. The substrate 24 has a
circular shape when viewed in the direction in which the rotary
shaft 23 extends. A phosphor layer 25 is provided on a first
surface 24a of the substrate 24 in the form of a ring along the
circumferential direction of the substrate 24. One location of the
ring-shaped phosphor layer 25 is irradiated with the excitation
light E. In FIG. 6, the area irradiated with the excitation light E
is labeled with the reference character C.
[0083] The wavelength conversion element 21 includes the substrate
24, a reflection mirror 26 (reflection section), a bonding layer 27
(bonding section), a low refractive index layer 28 (first
refractive index section), a high refractive index layer 29 (second
refractive index section), the phosphor layer 25 (wavelength
conversion section), and a refractive index interface 31 provided
with a plurality of prism structures 30, as shown in FIG. 2. The
reflection mirror 26, the bonding layer 27, the low refractive
index layer 28, the high refractive index layer 29, and the
phosphor layer 25 are layered on the first surface 24a (upper
surface) of the substrate 24 in this order from the side facing the
substrate 24. That is, the wavelength conversion element 21 further
includes the low refractive index layer 28, which is so provided
between the phosphor layer 25 and the bonding layer 27 as to be in
contact with the bonding layer 27, and the high refractive index
layer 29, which is so provided between the phosphor layer 25 and
the bonding layer 27 as to be in contact with the phosphor layer
25.
[0084] The phosphor layer 25 has a first surface 25a (upper
surface), on which the excitation light E is incident and through
which the fluorescence Y exits. That is, the wavelength conversion
element 21 is a reflective wavelength conversion element that emits
the fluorescence Y through the surface on which the excitation
light E is incident.
[0085] The substrate 24 is formed of a metal plate made, for
example, of copper or aluminum, which has relatively high thermal
conductivity. The substrate 24 has the function of supporting the
reflection mirror 26, the bonding layer 27, the low refractive
index layer 28, the high refractive index layer 29, and the
phosphor layer 25 and dissipating heat generated in the phosphor
layer 25. To enhance the heat dissipating function, a heat sink or
any other heat dissipating member may be provided on a second
surface 24b of the substrate 24.
[0086] The reflection mirror 26 is configured in the form of a
dielectric mirror formed of a dielectric multilayer film. The
reflection mirror 26 may instead be configured in the form of a
metal mirror formed of a metal thin film made, for example, of
silver. The reflection mirror 26 may be formed as a component
separate from the substrate 24 and glued to the first surface 24a
of the substrate 24 via an adhesive layer that is not shown or may
have a configuration in which a dielectric multilayer film or a
metal thin film is directly formed on the first surface 24a of the
substrate 24. The reflection mirror 26 reflects the fluorescence Y
traveling toward the substrate 24 out of the fluorescence Y emitted
from the phosphor layer 25 to cause the reflected fluorescence Y to
travel toward the phosphor layer 25 again. The upper surface of the
reflection mirror 26 is therefore a reflection surface 26a. The
reflection surface 26a of the reflection mirror 26 reflects the
fluorescence Y. That is, the wavelength conversion element 21
includes the substrate 24 so provided as to be in contact with the
reflection mirror 26.
[0087] The bonding layer 27 is made of a silicone adhesive having
light transparency. The bonding layer 27 bonds the substrate 24, on
which the reflection mirror 26 is provided, to a separately
produced laminate formed of the low refractive index layer 28, the
high refractive index layer 29, and the phosphor layer 25. That is,
the bonding layer 27 bonds the phosphor layer 25 and the reflection
mirror 26 to each other.
[0088] The low refractive index layer 28 and the high refractive
index layer 29 are each made of glass, resin, or any other material
having light transparency. The high refractive index layer 29 is
made of a first medium. The low refractive index layer 28 is made
of a second medium different from the first medium in terms of
medium type. That is, the surface where the low refractive index
layer 28 and the high refractive index layer 29 are in contact with
each other forms the refractive index interface 31, where the first
medium and the second medium, which have refractive indices
different from each other, are in contact with each other. The
refractive index interface 31 is formed of a surface which is
provided between the first surface 25a and the reflection surface
26a and where the first medium and the second medium, which have
refractive indices different from each other, are in contact with
each other. The refractive index of the first medium, which is
located on one side of the refractive index interface 31, the side
facing the first surface 25a, is higher than the refractive index
of the second medium, which is located on the other side of the
refractive index interface 31, the side facing the reflection
surface 26a.
[0089] FIG. 3A is a perspective view of the plurality of prism
structures 30. FIG. 3B is a plan view of the plurality of prism
structures 30 viewed in the direction of a normal to the reflection
surface 26a.
[0090] A prism array 33 formed of the plurality of prism structures
30 is provided along the refractive index interface 31 between the
low refractive index layer 28 and the high refractive index layer
29, as shown in FIGS. 2, 3A, and 3B. The prism array 33 has a
configuration in which the plurality of prism structures 30 are
arranged with no gap therebetween in a closest packing state. In
other words, the refractive index interface 31 is so shaped that a
plurality of inclining surfaces are continuously arranged with no
gap therebetween. The prism structures 30 are each a square pyramid
having a square bottom surface in the description byway of example
but may be a quadrilateral pyramid other than a square pyramid or a
polygonal pyramid other than a quadrilateral pyramid. That is, the
refractive index interface 31 is so shaped to contain a plurality
of pyramids. In this case, the pyramids each have a polygonal
bottom surface.
[0091] The plurality of prism structures 30 may have the same
dimension and shape or may have different dimensions and shapes. In
the case where the plurality of prism structures 30 may have the
same dimension and shape, the prism structures 30 are desirably
arranged at intervals P ranging, for example, from about several
micrometers to 50 micrometers. The prism structures 30 desirably
have a height T (distance from bottom surface to vertex) that is
desirably, for example, at least 0.2 times the arrangement interval
P described above.
[0092] FIG. 4A is a perspective view of a prism structure 50 in a
variation. FIG. 4B is a plan view of the prism structures 50 in the
variation viewed in the direction of a normal to the reflection
surface 26a.
[0093] The prism structure 50 in the variation is a cone as the
basis shape but is also so shaped that part of a bottom-side
portion of the cone is cut along flat planes parallel to the center
axis of the cone, as shown in FIGS. 4A and 4B. That is, the prism
structure 50 is so shaped that a portion thereof facing the vertex
50t has a conical shape and a portion thereof facing the bottom
surface 50b has a square shape. The bottom surface 50b of the prism
structure 50 may instead be a quadrilateral other than a square or
a polygon other than a quadrilateral.
[0094] The prism array 33 may be provided along the high refractive
index layer 29 or the low refractive index layer 28. In the case
where the prism array is provided along the high refractive index
layer 29, the prism array 33 can be produced in the step of
manufacturing the wavelength conversion element 21 as follows: A
die is used to form the high refractive index layer 29; the surface
shape of the die is transferred to the surface of a high refractive
index layer material to form the plurality of prism structures 30;
and the gaps between the prism structures 30 are filled with a low
refractive index layer material. The same holds true for the case
where the prism array 33 is provided along the low refractive index
layer 28.
[0095] The phosphor layer 25 is formed of a phosphor that is
excited with the excitation light E emitted from the first light
emitting device 10 and emits the yellow fluorescence Y. The
phosphor layer 25 contains a YAG-based phosphor made of
(Y,GD).sub.3(Al,Ga).sub.5O.sub.12(YAG:Ce), which is an inorganic
material, and an activator agent that is dispersed in the YAG
phosphor and serves as light emission centers. That is, in the
first embodiment, the phosphor layer 25 is formed of a YAG-based
phosphor made of (Y,GD).sub.3(Al,Ga).sub.5O.sub.12(YAG:Ce) having
Ce dispersed therein as the activator agent.
[0096] The phosphor layer 25 is not necessarily formed of a
YAG-based phosphor but is desirably formed of a garnet-based
phosphor. A garnet-based phosphor has thermal conductivity higher
than that of any other phosphor and has therefore higher
reliability in a high temperature environment. Therefore, even in a
case where the light source apparatus uses a stationary phosphor is
used in place of the rotating wheel, high-intensity fluorescence is
produced.
[0097] As an example of the refractive index, assume that the
refractive index of the phosphor layer 25 made of a YAG-based
phosphor is 1.8, and that the refractive index of the bonding layer
27 made of a silicone adhesive is 1.4. The materials of the low
refractive index layer 28 and the high refractive index layer 29
may be so selected from glass, resin, and other materials each
having a refractive index greater than 1.4 but smaller than 1.8
that the refractive index of the low refractive index layer 28 is
smaller than the refractive index of the high refractive index
layer 29.
[0098] The operation of the wavelength conversion element 21
according to the present embodiment will be described below with
reference to FIG. 5.
[0099] The fluorescence Y produced when the phosphor layer 25 is
irradiated with the excitation light E has no directivity and
therefore isotropically travels, as shown in FIG. 5. That is, the
light orientation distribution of the fluorescence Y is the
Lambertian distribution.
[0100] There is fluorescence Y that travels from an arbitrary light
emission point S in the phosphor layer 25 toward the first surface
25a (upper side in FIG. 5) and directly exits into the external
space, but fluorescence Y0, which travels from the light emission
point S toward the refractive index interface 31 (lower side in
FIG. 5) is now considered. Having traveled through the high
refractive index layer 29 and reached the refractive index
interface 31, the fluorescence Y0 is separated in accordance with
the angle of incidence thereof with respect to the refractive index
interface 31 into transmitted light Y1, which passes through the
refractive index interface 31, and reflected light Y2, which is
totally reflected off the refractive index interface 31.
[0101] The transmitted light Y1 is refracted at the refractive
index interface 31 in a direction in which the refracted light Y1
is incident on the reflection surface 26a at a smaller angle of
incidence. On the other hand, the reflected light Y2 is reflected
again off the portion of the refractive index interface 31
(inclining surface 31b) adjacent to the portion of the refractive
index interface 31 (inclining surface 31a) on which the
fluorescence Y0 has been incident for the first time, returns into
the phosphor layer 25, is scatteringly reflected off fine particles
and air holes in the phosphor layer 25, and is incident again on
the refractive index interface 31. To be exact, the entire
reflected light Y2 is not reflected again off the reflection
surfaces 31b, and part of the reflected light which is totally
reflected off the refractive index interface 31 (not shown) passes
through the inclining surface 31b. The light having passed through
the inclining surface 31b causes the light orientation distribution
to widen, but the amount of such light is limited. Further, the
prism structures 30 and 50 are desirably so designed as to minimize
the amount of such light.
[0102] As described above, the majority of the fluorescence Y0
emitted from the phosphor layer 25 toward the reflection surface
26a passes through the refractive index interface 31 and impinges
on the reflection mirror 26. In this process, there is light that
repeatedly undergoes multiple reflection between the phosphor layer
25 and the refractive index interface 31 and eventually impinges on
the reflection mirror 26, as described above. The passage of the
fluorescence Y0 emitted toward the reflection mirror 26 through the
refractive index interface 31 from the high refractive index medium
(first medium) toward the low refractive index medium (second
medium) increases the directivity of the fluorescence Y0, so that
the fluorescence Y0 is converted into fluorescence Y3 having a
narrower light orientation distribution, which is incident on the
reflection mirror 26. That is, the angular distribution of the
fluorescence Y3 having passed through the refractive index
interface 31 is narrower than the angular distribution of the
fluorescence Y0 before passing through the refractive index
interface 31.
[0103] The fluorescence Y3 having the narrower angular distribution
is reflected off the reflection mirror 26 and therefore returns
into the phosphor layer, and fluorescence Y4 reflected off the
reflection surface exits in the direction opposite the direction in
which the excitation light E has been incident through the first
surface 25a of the phosphor layer 25.
[0104] In both the case where the reflection mirror 26 is formed of
a dielectric mirror and the case where the reflection mirror 26 is
formed of a metal mirror, the reflectance of the fluorescence
depends on the angle of incidence thereof, and the greater the
angle of incidence, the lower the reflectance. A light source
apparatus of related art therefore has a problem of a wide angular
distribution of the fluorescence incident on the reflection mirror
and hence a decrease in the amount of reflected light.
[0105] To solve the problem described above, in the wavelength
conversion element 21 according to the present embodiment, which is
provided with the refractive index interface 31 including the prism
array 33, the angular distribution of the fluorescence Y incident
on the reflection mirror 26 is narrower than in a case where no
refractive index interface 31 is provided, whereby high reflectance
of the fluorescence Y is achieved, and a decrease in the amount of
reflected light can be suppressed. A wavelength conversion element
21 capable of producing high-optical-intensity fluorescence Y can
thus be achieved.
[0106] Further, a dielectric mirror has a high dependence of the
reflectance on the angle of incidence as compared with a metal
mirror but allows high reflectance as compared with a metal mirror
in a region of a narrow incident angle range and hence achieves low
reflection loss. A dielectric mirror is therefore preferably used
in combination with the refractive index interface 31 provided with
the prism array 33, whereby the efficiency of reflection of the
fluorescence Y can be increased by making use of the
characteristics of a dielectric multilayer film. Further, since the
amount of light absorbed by a dielectric mirror is smaller than the
amount of light absorbed by a metal mirror, even when
high-optical-intensity excitation light E is incident on the
dielectric mirror, degradation of the reflection mirror 26 can be
suppressed, whereby stable optical performance of the reflection
mirror 26 can be maintained for a long period.
[0107] Further, since the wavelength conversion element 21
according to the present embodiment includes the high refractive
index layer 29 and the low refractive index layer 28, appropriately
selecting the materials of the layers to adjust the refractive
indices of the high refractive index layer 29 and the low
refractive index layer 28 allows control of the angular
distribution of the fluorescence Y having passed through the
refractive index interface 31.
[0108] Since the wavelength conversion element 21 according to the
present embodiment includes a square pyramidal prism structures 30,
a symmetric angular distribution with respect to the direction of a
normal to the reflection surface 26a can be produced. Further,
since the plurality of prism structures 30 can be arranged in the
closest packing state, as shown in FIG. 3B, the effect of narrowing
the angular distribution of the fluorescence Y can be
maximized.
[0109] The first light source apparatus 100 according to the
present embodiment, which includes the wavelength conversion
element 21 having the effect described above, can produce
high-optical-intensity fluorescence and can therefore produce
high-intensity output light.
[0110] The projector 1 according to the present embodiment, which
includes the first light source apparatus 100 having the effect
described above, can produce a high-luminance projection image.
Second Embodiment
[0111] A second embodiment of the invention will be described below
with reference to FIG. 7.
[0112] A projector and a light source apparatus according to the
second embodiment are the same as those according to the first
embodiment in terms of basic configuration but differ therefrom in
terms of the configuration of the wavelength conversion element. No
overall description of the projector and the light source apparatus
is therefore made, and only the wavelength conversion element will
be described.
[0113] FIG. 7 is a cross-sectional view of the wavelength
conversion element according to the second embodiment.
[0114] In FIG. 7, components common to those in the drawings used
in the first embodiment have the same reference characters, and no
detailed description of the common components will be made.
[0115] A wavelength conversion element 41 includes the substrate
24, the reflection mirror 26 (reflection section), the bonding
layer 27 (bonding section), a low refractive index layer 42 (first
refractive index section), a phosphor layer (wavelength conversion
section), and a refractive index interface 45 provided with a
plurality of prism structures 44, as shown in FIG. 7. The
reflection mirror 26, the bonding layer 27, the low refractive
index layer 42, and the phosphor layer 43 are layered on the first
surface 24a of the substrate 24 in this order from the side facing
the substrate 24. That is, the wavelength conversion element 41
further includes the low refractive index layer 42 provided between
the phosphor layer 43 and the bonding layer 27.
[0116] The low refractive index layer 42 is made of glass, resin,
or any other material having light transparency. The low refractive
index layer 42 is made of the second medium different from the
medium of the phosphor layer 43 (first medium) in terms of
refractive index. That is, the surface where the phosphor layer 43
and the low refractive index layer 42 are in contact with each
other forms the refractive index interface 45, where the first
medium and the second medium, which have refractive indices
different from each other, are in contact with each other. The
refractive index of the first medium, which forms the phosphor
layer 43 located on one side of the refractive index interface 45,
the side facing a first surface 43a, is higher than the refractive
index of the second medium, which forms the low refractive index
layer 42 located on the other side of the refractive index
interface 45, the side facing the reflection surface 26a. The
phosphor layer 43 in the second embodiment therefore operates as
both the phosphor layer 25 and the high refractive index layer 29
in the first embodiment.
[0117] A prism array 46 formed of the plurality of prism structures
44 is provided along the refractive index interface 45 between the
phosphor layer 43 and the low refractive index layer 42. The prism
structures 44 and the prism array 46 are configured in the same
manner as in the first embodiment. The prism array 46 may be
provided on the phosphor layer 43 or the low refractive index layer
42. In the case where the prism array 46 is provided on the
phosphor layer 43, the prism array 46 can be produced in the step
of manufacturing the wavelength conversion element 41, for example,
by etching a second surface 43b of the phosphor layer 43.
[0118] The other configurations of the prism array 46 are the same
as those in the first embodiment.
[0119] In the wavelength conversion element 41 according to the
second embodiment, since the refractive index interface 45
including the prism array 46 is provided, and the first medium,
which forms the base material of the phosphor layer 43, has a
refractive index higher than that of the second medium, which forms
the low refractive index layer 42, the angular distribution of the
fluorescence Y incident on the reflection mirror 26 can be
narrowed, whereby high reflectance is achieved at the reflection
mirror 26, and a decrease in the amount of reflected light can
therefore be suppressed, as in the first embodiment. A wavelength
conversion element 41 capable of producing high-optical-intensity
fluorescence Y can thus be achieved.
[0120] Further, also in the second embodiment, use of a dielectric
mirror advantageously allows suppression of degradation of the
reflection mirror 26, as in the first embodiment.
[0121] In the second embodiment, in which no high refractive index
layer 29 is used, unlike in the first embodiment, the number of
layers that form the wavelength conversion element 41 can be
reduced, as compared with the first embodiment. The cost of the
wavelength conversion element 41 can therefore be reduced.
Third Embodiment
[0122] A third embodiment of the invention will be described below
with reference to FIG. 8.
[0123] A projector and a light source apparatus according to the
third embodiment are the same as those according to the first
embodiment in terms of basic configuration but differ therefrom in
terms of the configuration of the wavelength conversion element. No
overall description of the projector and the light source apparatus
is therefore made, and only the wavelength conversion element will
be described.
[0124] FIG. 8 is a cross-sectional view of the wavelength
conversion element according to the third embodiment.
[0125] In FIG. 8, components common to those in the drawings used
in the first embodiment have the same reference characters, and no
detailed description of the common components will be made.
[0126] A wavelength conversion element 61 includes the substrate
24, the reflection mirror 26 (reflection section), a bonding layer
62 (bonding section), the high refractive index layer 29 (second
refractive index section), the phosphor layer (wavelength
conversion section), and a refractive index interface 65 provided
with a plurality of prism structures 64, as shown in FIG. 8. The
reflection mirror 26, the bonding layer 62, the high refractive
index layer 29, and the phosphor layer 25 are layered on the first
surface 24a of the substrate 24 in this order from the side facing
the substrate 24. That is, the wavelength conversion element 61
further includes the high refractive index layer 29 provided
between the phosphor layer 25 and the bonding layer 62.
[0127] The high refractive index layer 29 is made of glass, resin,
or any other material having light transparency. The high
refractive index layer 29 is made of the first medium different
from the second medium, which forms the bonding layer 62, in terms
of refractive index. That is, the surface where the high refractive
index layer 29 and the bonding layer 62 are in contact with each
other forms the refractive index interface 65, where the first
medium and the second medium, which have refractive indices
different from each other, are in contact with each other. The
refractive index of the first medium, which forms the high
refractive index layer 29 located on one side of the refractive
index interface 65, the side facing the first surface 25a, is
higher than the refractive index of the second medium, which forms
the bonding layer 62 located on the other side of the refractive
index interface 65, the side facing the reflection surface 26a. The
bonding layer 62 in the third embodiment therefore operates as both
the low refractive index layer 28 and the bonding layer 27 in the
first embodiment. The refractive index interface 65 may instead be
formed of a first surface 62a of the bonding layer 62, the surface
thereof located on the side facing the phosphor layer 25.
[0128] A prism array 66 formed of the plurality of prism structures
64 is provided along the refractive index interface 65 between the
high refractive index layer 29 and the bonding layer 62. The prism
structures 64 and the prism array 66 are configured in the same
manner as in the first embodiment. The prism array 66 may be
provided on the high refractive index layer 29 or the bonding layer
62.
[0129] The other configurations of the prism array 66 are the same
as those in the first embodiment.
[0130] In the wavelength conversion element 61 according to the
third embodiment, since the refractive index interface 65 provided
with the prism array 66 is provided, and the first medium, which
forms the high refractive index layer 29, has a refractive index
higher than that of the second medium, which forms the bonding
layer 62, the angular distribution of the fluorescence Y incident
on the reflection mirror 26 can be narrowed, whereby high
reflectance is achieved at the reflection mirror 26, and a decrease
in the amount of reflected light can therefore be suppressed, as in
the first embodiment. A wavelength conversion element 61 capable of
producing high-optical-intensity fluorescence Y can thus be
achieved.
[0131] Also in the third embodiment, use of a dielectric mirror
advantageously allows suppression of degradation of the reflection
mirror 26, as in the first embodiment.
[0132] In the third embodiment, in which no low refractive index
layer 28 is used, unlike in the first embodiment, the number of
layers that form the wavelength conversion element 61 can be
reduced, as compared with the first embodiment. The cost of the
wavelength conversion element 61 can therefore be reduced.
Fourth Embodiment
[0133] A fourth embodiment of the invention will be described below
with reference to FIG. 9.
[0134] A projector and a light source apparatus according to the
fourth embodiment are the same as those according to the first
embodiment in terms of basic configuration but differ therefrom in
terms of the configuration of the wavelength conversion element. No
overall description of the projector and the light source apparatus
is therefore made, and only the wavelength conversion element will
be described.
[0135] FIG. 9 is a cross-sectional view of the wavelength
conversion element according to the fourth embodiment.
[0136] In FIG. 9, components common to those in the drawings used
in the first to third embodiments have the same reference
characters, and no detailed description of the common components
will be made.
[0137] A wavelength conversion element 81 includes the substrate
24, the reflection mirror 26 (reflection section), the bonding
layer 62 (bonding section), the phosphor layer 43 (wavelength
conversion section), and a refractive index interface 85 provided
with a plurality of prism structures 84, as shown in FIG. 9. The
reflection mirror 26, the bonding layer 62, and the phosphor layer
43 are layered on the first surface 24a of the substrate 24 in this
order from the side facing the substrate 24.
[0138] The surface where the phosphor layer 43 and the bonding
layer 62 are in contact with each other forms the refractive index
interface 85, where the first medium and the second medium, which
have refractive indices different from each other, are in contact
with each other. In other words, the refractive index interface 85
is formed of the second surface 43b of the phosphor layer 43, the
surface thereof opposite the first surface 43a, or the first
surface 62a of the bonding layer 62, the surface thereof facing the
phosphor layer 43. The refractive index of the phosphor layer 43
(first medium) located on one side of the refractive index
interface 85, the side facing the first surface 43a, is higher than
the refractive index of the second medium, which forms the bonding
layer 62 located on the other side of the refractive index
interface 85, the side facing the reflection surface 26a.
[0139] A prism array 86 formed of the plurality of prism structures
84 is provided along the refractive index interface 85 between the
phosphor layer 43 and the bonding layer 62. The prism array 86 is
configured in the same manner as in the first embodiment. The prism
array 86 maybe provided on the phosphor layer 43 or the bonding
layer 62.
[0140] The other configurations of the prism array 86 are the same
as those in the first embodiment.
[0141] In the wavelength conversion element 81 according to the
fourth embodiment, since the refractive index interface 85
including the prism array 86 is provided, and the base material
(first medium), which forms the phosphor layer 43, has a refractive
index higher than that of the second medium, which forms the
bonding layer 62, the angular distribution of the fluorescence Y
incident on the reflection mirror 26 can be narrowed, whereby high
reflectance is achieved at the reflection mirror 26, and a decrease
in the amount of reflected light can therefore be suppressed, as in
the first embodiment. A wavelength conversion element 81 capable of
producing high-optical-intensity fluorescence Y can thus be
achieved.
[0142] Also in the fourth embodiment, use of a dielectric mirror
advantageously allows suppression of degradation of the reflection
mirror 26, as in the first embodiment.
[0143] Further, in the fourth embodiment, in which no high
refractive index layer 29 or low refractive index layer 28 is used,
unlike in the first embodiment, the number of layers that form the
wavelength conversion element 81 can be further educed, as compared
with the second and third embodiments. The cost of the wavelength
conversion element 81 can therefore be reduced.
Fifth Embodiment
[0144] A fifth embodiment of the invention will be described below
with reference to FIG. 10.
[0145] A projector and a light source apparatus according to the
fifth embodiment are the same as those according to the first
embodiment in terms of basic configuration but differ therefrom in
that the configuration of the wavelength conversion apparatus
differs from the configuration of the wavelength conversion
apparatus 20 in the first embodiment. No overall description of the
projector and the light source apparatus is therefore made, and
only the wavelength conversion apparatus will be described.
[0146] FIG. 10 is a schematic configuration diagram of the
projector according to the fifth embodiment.
[0147] In FIG. 10, components common to those in the drawings used
in the first embodiment have the same reference characters, and no
detailed description of the common components will be made.
[0148] The wavelength conversion apparatus 20 of the first light
source apparatus 100 according to the first embodiment includes a
disk-shaped wavelength conversion element 21 rotatable with the
motor 22. In contrast, in a projector 3 according to the fifth
embodiment, a first light source apparatus 105 includes a
stationary wavelength conversion element 81 (wavelength conversion
apparatus 81), as shown in FIG. 10. The wavelength conversion
element 81 has, for example, a rectangular shape when viewed in the
direction of a normal to a substrate 82. The wavelength conversion
element 81 can be a wavelength conversion element having the same
cross-sectional structure as any of those of the wavelength
conversion elements 21, 41, 61, and 81 shown in the first to fourth
embodiments by way of example. It is, however, noted that a heat
sink 83 may be provided on the substrate 82 to enhance the heat
dissipation effect.
[0149] The fifth embodiment also provides the same advantageous
effects as those provided by the first embodiment as follows: The
wavelength conversion element 81 capable of producing
high-optical-intensity fluorescence can be achieved; use of a
dielectric mirror suppresses degradation of the reflection mirror;
the first light source apparatus 100 capable of producing
high-intensity output light can be achieved; and a projector 3
capable of producing a high-luminance projection image can be
achieved.
[0150] The technical scope of the invention is not limited to the
embodiments described above, and a variety of changes can be made
thereto to the extent that the changes do not depart from the
substance of the invention.
[0151] For example, in the embodiments described above, the case
where a plurality of prism structures all having the same shape and
dimension are provided on the refractive index interface has been
presented by way of example. In place of this configuration, a
plurality of pyramidal prism structures having different shapes or
dimensions maybe provided. In this case, there is a case where the
plurality of prism structures cannot be arranged in the closest
packing state, and the refractive index interface therefore has a
flat surface portion parallel to the reflection surface. In this
configuration, the effect of narrowing the angular distribution of
the fluorescence decreases as compared with the configuration in
each of the embodiments described above. However, high-intensity
fluorescence can be produced as compared with a wavelength
conversion element of related art.
[0152] A layer other than the layers presented by way of example in
the embodiments described above maybe added to the wavelength
conversion element according to each of the embodiments of the
invention. For example, an antireflection layer may be provided on
the excitation-light-incident-side first surface of the phosphor
layer.
[0153] In addition, the number, shape, material, arrangement, and
other factors of each of the components that form the wavelength
conversion element and the light source apparatus can be changed as
appropriate. In the embodiments described above, the projector
including the three light modulators is presented by way of
example. Instead, the invention is also applicable to a projector
that displays color video images via a single light modulator.
Further, as each of the light modulators, the liquid crystal panel
described above is not necessarily used, and a digital mirror
device can, for example, be used.
[0154] The shape, number, arrangement, material, and other factors
of each of the components of the projector are not limited to those
in the embodiments described above and can be changed as
appropriate.
[0155] Further, in the embodiments described above, the case where
the light source apparatus according to any of the embodiments of
the invention is incorporated in a projector is presented, but not
necessarily. The light source apparatus according to any of the
embodiments of the invention can also be used, for example, as a
lighting apparatus and an automobile headlight.
[0156] The entire disclosure of Japanese Patent Application No.
2017-063251, filed on Mar. 28, 2017 is expressly incorporated by
reference herein.
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